Auto merge of #16224 - servo:valid-fontface, r=upsuper

Make the parser accept @font-face rules without font-family or src.

Fix #16165.

Also, it turns out that the CSSFontFaceRule IDL specified in the css-fonts spec is not web-compatible. Instead browsers implement a .style attribute like in CSSStyleRule: https://github.com/w3c/csswg-drafts/issues/825

This in turn requires preserving data about which descriptors were set or not (distinguishing unset from set to a value that happens to be the initial value), so this commit also makes every field `Option<_>`.

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1 files changed, 16 insertions, 12 deletions

diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 74c95499006..abc0a5e771a 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -355,20 +355,24 @@ fn add_font_face_rules(stylesheet: &Stylesheet,
                        outstanding_web_fonts_counter: &Arc<AtomicUsize>) {
     if opts::get().load_webfonts_synchronously {
         let (sender, receiver) = ipc::channel().unwrap();
-        stylesheet.effective_font_face_rules(&device, guard, |font_face| {
-            let effective_sources = font_face.effective_sources();
-            font_cache_thread.add_web_font(font_face.family.clone(),
-                                           effective_sources,
-                                           sender.clone());
-            receiver.recv().unwrap();
+        stylesheet.effective_font_face_rules(&device, guard, |rule| {
+            if let Some(font_face) = rule.font_face() {
+                let effective_sources = font_face.effective_sources();
+                font_cache_thread.add_web_font(font_face.family().clone(),
+                                               effective_sources,
+                                               sender.clone());
+                receiver.recv().unwrap();
+            }
         })
     } else {
-        stylesheet.effective_font_face_rules(&device, guard, |font_face| {
-            let effective_sources = font_face.effective_sources();
-            outstanding_web_fonts_counter.fetch_add(1, Ordering::SeqCst);
-            font_cache_thread.add_web_font(font_face.family.clone(),
-                                          effective_sources,
-                                          (*font_cache_sender).clone());
+        stylesheet.effective_font_face_rules(&device, guard, |rule| {
+            if let Some(font_face) = rule.font_face() {
+                let effective_sources = font_face.effective_sources();
+                outstanding_web_fonts_counter.fetch_add(1, Ordering::SeqCst);
+                font_cache_thread.add_web_font(font_face.family().clone(),
+                                              effective_sources,
+                                              (*font_cache_sender).clone());
+            }
         })
     }
 }